/*
 * jdmerge.c
 *
 * Copyright (C) 1994-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains code for merged upsampling/color conversion.
 *
 * This file combines functions from jdsample.c and jdcolor.c;
 * read those files first to understand what's going on.
 *
 * When the chroma components are to be upsampled by simple replication
 * (ie, box filtering), we can save some work in color conversion by
 * calculating all the output pixels corresponding to a pair of chroma
 * samples at one time.  In the conversion equations
 *	R = Y           + K1 * Cr
 *	G = Y + K2 * Cb + K3 * Cr
 *	B = Y + K4 * Cb
 * only the Y term varies among the group of pixels corresponding to a pair
 * of chroma samples, so the rest of the terms can be calculated just once.
 * At typical sampling ratios, this eliminates half or three-quarters of the
 * multiplications needed for color conversion.
 *
 * This file currently provides implementations for the following cases:
 *	YCbCr => RGB color conversion only.
 *	Sampling ratios of 2h1v or 2h2v.
 *	No scaling needed at upsample time.
 *	Corner-aligned (non-CCIR601) sampling alignment.
 * Other special cases could be added, but in most applications these are
 * the only common cases.  (For uncommon cases we fall back on the more
 * general code in jdsample.c and jdcolor.c.)
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"

#ifdef UPSAMPLE_MERGING_SUPPORTED


/* Private subobject */

typedef struct {
    struct jpeg_upsampler pub;  /* public fields */

    /* Pointer to routine to do actual upsampling/conversion of one row group */
    JMETHOD( void, upmethod, ( j_decompress_ptr cinfo,
                               JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
                               JSAMPARRAY output_buf ) );

    /* Private state for YCC->RGB conversion */
    int *   Cr_r_tab;   /* => table for Cr to R conversion */
    int *   Cb_b_tab;   /* => table for Cb to B conversion */
    INT32 * Cr_g_tab;   /* => table for Cr to G conversion */
    INT32 * Cb_g_tab;   /* => table for Cb to G conversion */

    /* For 2:1 vertical sampling, we produce two output rows at a time.
     * We need a "spare" row buffer to hold the second output row if the
     * application provides just a one-row buffer; we also use the spare
     * to discard the dummy last row if the image height is odd.
     */
    JSAMPROW spare_row;
    boolean  spare_full;    /* T if spare buffer is occupied */

    JDIMENSION out_row_width;/* samples per output row */
    JDIMENSION rows_to_go;  /* counts rows remaining in image */
} my_upsampler;

typedef my_upsampler * my_upsample_ptr;

#define SCALEBITS   16  /* speediest right-shift on some machines */
#define ONE_HALF    ( (INT32) 1 << ( SCALEBITS - 1 ) )
#define FIX( x )      ( (INT32) ( ( x ) * ( 1L << SCALEBITS ) + 0.5 ) )


/*
 * Initialize tables for YCC->RGB colorspace conversion.
 * This is taken directly from jdcolor.c; see that file for more info.
 */

LOCAL void
build_ycc_rgb_table( j_decompress_ptr cinfo ) {
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    int i;
    INT32 x;
    SHIFT_TEMPS

    upsample->Cr_r_tab = (int *)
                         ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                      ( MAXJSAMPLE + 1 ) * SIZEOF( int ) );
    upsample->Cb_b_tab = (int *)
                         ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                      ( MAXJSAMPLE + 1 ) * SIZEOF( int ) );
    upsample->Cr_g_tab = (INT32 *)
                         ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                      ( MAXJSAMPLE + 1 ) * SIZEOF( INT32 ) );
    upsample->Cb_g_tab = (INT32 *)
                         ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                      ( MAXJSAMPLE + 1 ) * SIZEOF( INT32 ) );

    for ( i = 0, x = -CENTERJSAMPLE; i <= MAXJSAMPLE; i++, x++ ) {
        /* i is the actual input pixel value, in the range 0..MAXJSAMPLE */
        /* The Cb or Cr value we are thinking of is x = i - CENTERJSAMPLE */
        /* Cr=>R value is nearest int to 1.40200 * x */
        upsample->Cr_r_tab[i] = (int)
                                RIGHT_SHIFT( FIX( 1.40200 ) * x + ONE_HALF, SCALEBITS );
        /* Cb=>B value is nearest int to 1.77200 * x */
        upsample->Cb_b_tab[i] = (int)
                                RIGHT_SHIFT( FIX( 1.77200 ) * x + ONE_HALF, SCALEBITS );
        /* Cr=>G value is scaled-up -0.71414 * x */
        upsample->Cr_g_tab[i] = ( -FIX( 0.71414 ) ) * x;
        /* Cb=>G value is scaled-up -0.34414 * x */
        /* We also add in ONE_HALF so that need not do it in inner loop */
        upsample->Cb_g_tab[i] = ( -FIX( 0.34414 ) ) * x + ONE_HALF;
    }
}


/*
 * Initialize for an upsampling pass.
 */

METHODDEF void
start_pass_merged_upsample( j_decompress_ptr cinfo ) {
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

    /* Mark the spare buffer empty */
    upsample->spare_full = FALSE;
    /* Initialize total-height counter for detecting bottom of image */
    upsample->rows_to_go = cinfo->output_height;
}


/*
 * Control routine to do upsampling (and color conversion).
 *
 * The control routine just handles the row buffering considerations.
 */

METHODDEF void
merged_2v_upsample( j_decompress_ptr cinfo,
                    JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
                    JDIMENSION in_row_groups_avail,
                    JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
                    JDIMENSION out_rows_avail ) {
/* 2:1 vertical sampling case: may need a spare row. */
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    JSAMPROW work_ptrs[2];
    JDIMENSION num_rows;    /* number of rows returned to caller */

    if ( upsample->spare_full ) {
        /* If we have a spare row saved from a previous cycle, just return it. */
        jcopy_sample_rows( &upsample->spare_row, 0, output_buf + *out_row_ctr, 0,
                           1, upsample->out_row_width );
        num_rows = 1;
        upsample->spare_full = FALSE;
    } else {
        /* Figure number of rows to return to caller. */
        num_rows = 2;
        /* Not more than the distance to the end of the image. */
        if ( num_rows > upsample->rows_to_go ) {
            num_rows = upsample->rows_to_go;
        }
        /* And not more than what the client can accept: */
        out_rows_avail -= *out_row_ctr;
        if ( num_rows > out_rows_avail ) {
            num_rows = out_rows_avail;
        }
        /* Create output pointer array for upsampler. */
        work_ptrs[0] = output_buf[*out_row_ctr];
        if ( num_rows > 1 ) {
            work_ptrs[1] = output_buf[*out_row_ctr + 1];
        } else {
            work_ptrs[1] = upsample->spare_row;
            upsample->spare_full = TRUE;
        }
        /* Now do the upsampling. */
        ( *upsample->upmethod )( cinfo, input_buf, *in_row_group_ctr, work_ptrs );
    }

    /* Adjust counts */
    *out_row_ctr += num_rows;
    upsample->rows_to_go -= num_rows;
    /* When the buffer is emptied, declare this input row group consumed */
    if ( !upsample->spare_full ) {
        ( *in_row_group_ctr )++;
    }
}


METHODDEF void
merged_1v_upsample( j_decompress_ptr cinfo,
                    JSAMPIMAGE input_buf, JDIMENSION * in_row_group_ctr,
                    JDIMENSION in_row_groups_avail,
                    JSAMPARRAY output_buf, JDIMENSION * out_row_ctr,
                    JDIMENSION out_rows_avail ) {
/* 1:1 vertical sampling case: much easier, never need a spare row. */
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;

    /* Just do the upsampling. */
    ( *upsample->upmethod )( cinfo, input_buf, *in_row_group_ctr,
                             output_buf + *out_row_ctr );
    /* Adjust counts */
    ( *out_row_ctr )++;
    ( *in_row_group_ctr )++;
}


/*
 * These are the routines invoked by the control routines to do
 * the actual upsampling/conversion.  One row group is processed per call.
 *
 * Note: since we may be writing directly into application-supplied buffers,
 * we have to be honest about the output width; we can't assume the buffer
 * has been rounded up to an even width.
 */


/*
 * Upsample and color convert for the case of 2:1 horizontal and 1:1 vertical.
 */

METHODDEF void
h2v1_merged_upsample( j_decompress_ptr cinfo,
                      JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
                      JSAMPARRAY output_buf ) {
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    register int y, cred, cgreen, cblue;
    int cb, cr;
    register JSAMPROW outptr;
    JSAMPROW inptr0, inptr1, inptr2;
    JDIMENSION col;
    /* copy these pointers into registers if possible */
    register JSAMPLE * range_limit = cinfo->sample_range_limit;
    int * Crrtab = upsample->Cr_r_tab;
    int * Cbbtab = upsample->Cb_b_tab;
    INT32 * Crgtab = upsample->Cr_g_tab;
    INT32 * Cbgtab = upsample->Cb_g_tab;
    SHIFT_TEMPS

    inptr0 = input_buf[0][in_row_group_ctr];
    inptr1 = input_buf[1][in_row_group_ctr];
    inptr2 = input_buf[2][in_row_group_ctr];
    outptr = output_buf[0];
    /* Loop for each pair of output pixels */
    for ( col = cinfo->output_width >> 1; col > 0; col-- ) {
        /* Do the chroma part of the calculation */
        cb = GETJSAMPLE( *inptr1++ );
        cr = GETJSAMPLE( *inptr2++ );
        cred = Crrtab[cr];
        cgreen = (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr], SCALEBITS );
        cblue = Cbbtab[cb];
        /* Fetch 2 Y values and emit 2 pixels */
        y  = GETJSAMPLE( *inptr0++ );
        outptr[RGB_RED] =   range_limit[y + cred];
        outptr[RGB_GREEN] = range_limit[y + cgreen];
        outptr[RGB_BLUE] =  range_limit[y + cblue];
        outptr += RGB_PIXELSIZE;
        y  = GETJSAMPLE( *inptr0++ );
        outptr[RGB_RED] =   range_limit[y + cred];
        outptr[RGB_GREEN] = range_limit[y + cgreen];
        outptr[RGB_BLUE] =  range_limit[y + cblue];
        outptr += RGB_PIXELSIZE;
    }
    /* If image width is odd, do the last output column separately */
    if ( cinfo->output_width & 1 ) {
        cb = GETJSAMPLE( *inptr1 );
        cr = GETJSAMPLE( *inptr2 );
        cred = Crrtab[cr];
        cgreen = (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr], SCALEBITS );
        cblue = Cbbtab[cb];
        y  = GETJSAMPLE( *inptr0 );
        outptr[RGB_RED] =   range_limit[y + cred];
        outptr[RGB_GREEN] = range_limit[y + cgreen];
        outptr[RGB_BLUE] =  range_limit[y + cblue];
    }
}


/*
 * Upsample and color convert for the case of 2:1 horizontal and 2:1 vertical.
 */

METHODDEF void
h2v2_merged_upsample( j_decompress_ptr cinfo,
                      JSAMPIMAGE input_buf, JDIMENSION in_row_group_ctr,
                      JSAMPARRAY output_buf ) {
    my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
    register int y, cred, cgreen, cblue;
    int cb, cr;
    register JSAMPROW outptr0, outptr1;
    JSAMPROW inptr00, inptr01, inptr1, inptr2;
    JDIMENSION col;
    /* copy these pointers into registers if possible */
    register JSAMPLE * range_limit = cinfo->sample_range_limit;
    int * Crrtab = upsample->Cr_r_tab;
    int * Cbbtab = upsample->Cb_b_tab;
    INT32 * Crgtab = upsample->Cr_g_tab;
    INT32 * Cbgtab = upsample->Cb_g_tab;
    SHIFT_TEMPS

    inptr00 = input_buf[0][in_row_group_ctr * 2];
    inptr01 = input_buf[0][in_row_group_ctr * 2 + 1];
    inptr1 = input_buf[1][in_row_group_ctr];
    inptr2 = input_buf[2][in_row_group_ctr];
    outptr0 = output_buf[0];
    outptr1 = output_buf[1];
    /* Loop for each group of output pixels */
    for ( col = cinfo->output_width >> 1; col > 0; col-- ) {
        /* Do the chroma part of the calculation */
        cb = GETJSAMPLE( *inptr1++ );
        cr = GETJSAMPLE( *inptr2++ );
        cred = Crrtab[cr];
        cgreen = (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr], SCALEBITS );
        cblue = Cbbtab[cb];
        /* Fetch 4 Y values and emit 4 pixels */
        y  = GETJSAMPLE( *inptr00++ );
        outptr0[RGB_RED] =   range_limit[y + cred];
        outptr0[RGB_GREEN] = range_limit[y + cgreen];
        outptr0[RGB_BLUE] =  range_limit[y + cblue];
        outptr0 += RGB_PIXELSIZE;
        y  = GETJSAMPLE( *inptr00++ );
        outptr0[RGB_RED] =   range_limit[y + cred];
        outptr0[RGB_GREEN] = range_limit[y + cgreen];
        outptr0[RGB_BLUE] =  range_limit[y + cblue];
        outptr0 += RGB_PIXELSIZE;
        y  = GETJSAMPLE( *inptr01++ );
        outptr1[RGB_RED] =   range_limit[y + cred];
        outptr1[RGB_GREEN] = range_limit[y + cgreen];
        outptr1[RGB_BLUE] =  range_limit[y + cblue];
        outptr1 += RGB_PIXELSIZE;
        y  = GETJSAMPLE( *inptr01++ );
        outptr1[RGB_RED] =   range_limit[y + cred];
        outptr1[RGB_GREEN] = range_limit[y + cgreen];
        outptr1[RGB_BLUE] =  range_limit[y + cblue];
        outptr1 += RGB_PIXELSIZE;
    }
    /* If image width is odd, do the last output column separately */
    if ( cinfo->output_width & 1 ) {
        cb = GETJSAMPLE( *inptr1 );
        cr = GETJSAMPLE( *inptr2 );
        cred = Crrtab[cr];
        cgreen = (int) RIGHT_SHIFT( Cbgtab[cb] + Crgtab[cr], SCALEBITS );
        cblue = Cbbtab[cb];
        y  = GETJSAMPLE( *inptr00 );
        outptr0[RGB_RED] =   range_limit[y + cred];
        outptr0[RGB_GREEN] = range_limit[y + cgreen];
        outptr0[RGB_BLUE] =  range_limit[y + cblue];
        y  = GETJSAMPLE( *inptr01 );
        outptr1[RGB_RED] =   range_limit[y + cred];
        outptr1[RGB_GREEN] = range_limit[y + cgreen];
        outptr1[RGB_BLUE] =  range_limit[y + cblue];
    }
}


/*
 * Module initialization routine for merged upsampling/color conversion.
 *
 * NB: this is called under the conditions determined by use_merged_upsample()
 * in jdmaster.c.  That routine MUST correspond to the actual capabilities
 * of this module; no safety checks are made here.
 */

GLOBAL void
jinit_merged_upsampler( j_decompress_ptr cinfo ) {
    my_upsample_ptr upsample;

    upsample = (my_upsample_ptr)
               ( *cinfo->mem->alloc_small )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                            SIZEOF( my_upsampler ) );
    cinfo->upsample = (struct jpeg_upsampler *) upsample;
    upsample->pub.start_pass = start_pass_merged_upsample;
    upsample->pub.need_context_rows = FALSE;

    upsample->out_row_width = cinfo->output_width * cinfo->out_color_components;

    if ( cinfo->max_v_samp_factor == 2 ) {
        upsample->pub.upsample = merged_2v_upsample;
        upsample->upmethod = h2v2_merged_upsample;
        /* Allocate a spare row buffer */
        upsample->spare_row = (JSAMPROW)
                              ( *cinfo->mem->alloc_large )( (j_common_ptr) cinfo, JPOOL_IMAGE,
                                                           (size_t) ( upsample->out_row_width * SIZEOF( JSAMPLE ) ) );
    } else {
        upsample->pub.upsample = merged_1v_upsample;
        upsample->upmethod = h2v1_merged_upsample;
        /* No spare row needed */
        upsample->spare_row = NULL;
    }

    build_ycc_rgb_table( cinfo );
}

#endif /* UPSAMPLE_MERGING_SUPPORTED */
